Nailor Product 0722 Ceiling Dampers are for use in spherical purposes, in lieu of hinged doorway form dampers in any UL/ULC flooring/ceiling or roof/ceiling assembly with nearly a 3 hour fireplace resistance rating exactly where air ducts are permitted. Measurements available are constrained only through the process style and on-site space envelope limitations. Examples https://keeganoethu.blogunteer.com/35787035/the-fact-about-dampers-for-industrial-sector-that-no-one-is-suggesting